A sudden jump in the population of a rare mosquito in the area could mean trouble for household pets, vector control officials said this week.

So far this season, the San Gabriel Valley Mosquito and Vector Control District trapped 300 western tree hole mosquitoes.

Before this season, the district captured only 60 since it started collecting data 17 years ago, district spokeswoman Kelly Middleton said.

The agency covers neighborhoods from Altadena to Claremont south to areas near the 60 Freeway.

Unlike the dozen or so other species of mosquitoes found in Los Angeles County, the western tree hole mosquito is a frequent carrier of heartworm, said Dr. Emily Beeler of the Count’s Department of Public Health.

“Last year, we had many more cases reported than in previous years,” Beeler said. “More and more of those cases were thought to be locally contracted.”

Exactly why there are more tree hole mosquitoes this year is hard to say.

“In the history of this district, we’re lucky to catch any,” Middleton said. But “the increased rainfall we’ve had this year probably filled up tree holes.”

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